I just finished reading "As a good bartender might" by Thomas W. Polger, in which he enquires into whether whiskey and varieties of whiskeys are natural kinds. His answer, disappointingly, is that they might but he isn't sure: "I'm sure that not every distinction drawn among beverages qualifies them as natural kinds, but I would like to think that whiskey - bourbon in particular - is one of them."

He suggests, sensibly, that whiskies might be divided into natural kinds in terms of their ingredients: barley, rye, wheat, or corn. Although barley and corn plants form distinct natural kinds, they might still not underwrite separate beverage kinds. The matter is complicated by the fact that many whiskies use some combination of ingredients. Bourbon, for example, is predominantly but not entirely corn based.

He spends most of his attention, though, on whether place of origin divides whiskies into natural kinds. This is how liquor stores (and Wikipedia) divvy things up, but it seems like a non-starter to me. I have always counted Irish and Canadian whiskies in the same partition of whisky state space, along with blended Scotch. A more important division, which Polger doesn't discuss, is between blended whiskies and single malt or single batch whiskies.

I think that the difference between blended and single batch tracks an important culinary distinction. It seems to me that there are two different ideals in whiskey, distinct standards according to which whiskey might be judged and heights to which it can aspire. One is the smooth and crisp whiskey, best exemplified by fine blended whiskies. The other is the deep and weighty whiskey, exemplified by a peaty single malt Scotch (although it can be realized in other ways).

My father is rather fond of Johnny Walker Blue Label. To me, it exemplifies the first ideal. I have had it, and I can recognize its excellence for what it is. I am unimpressed not because it isn't good but because I think it chases the wrong dream. It's wasted on me. My dad, for his part, prefers Blue Label to any single malt Scotch. This difference between us is explicable in terms of the distinction between two different kinds of Scotch; the different kinds have different corresponding standards of goodness, different basins of attraction in beverage space.

This distinction cuts across ingredients. It also separates blended from single-batch bourbon. So too for rye.

Although differences in tastes are about the responses of drinkers, whiskey is a beverage. Natural kinds are always domain-relative. If we ask whether whiskies comprise natural kinds, then the proper domain should include agriculture, distilling, and drinking.

I'm not sure whether whiskies do comprise natural kinds, but the blended/single-batch (smooth/deep) divide strikes me as a plausible candidate.